This may shock both Oneness Pentecostals and Trinitarians, but the original Nicene Creed of 325 AD is not explicitly Trinitarian. Both Oneness Pentecostals and Trinitarians could subscribe to it; because Modalism actually contributed to the development of the Nicene Creed.
Shortly after I was born again in a Oneness Pentecostal Church, I was told that the Nicene Creed is a Trinitarian Creed that is against the Bible. Oneness Pentecostals commonly share the gospel with people by condemning the Nicene Creed as an explicit Trinitarian Creed, so I myself did the same until I took Bible College Courses by David Bernard back in the early 90’s. I do not remember his exact words verbatim, but I do remember him saying something about the early Nicene Creed not being explicitly Trinitarian so that Oneness believers may have also affirmed that creed. Dr. Bernard said the same about the early Apostles Creed. I’m not certain that Brother Bernard said it exactly the way I’m recalling it, but I’m very certain that he said that it was not explicitly Trinitarian and that the formulation of One God in three persons had not been fully developed until the fifth century. David Bernard’s comments about the early Nicene Creed surprised me because I had always thought that the Nicene Creed was solely a Trinitarian Creed.
The Council of Nicaea was convened in the Eastern Roman Empire, in present day Turkey.
Early Modalists Signed the Nicene Creed of 325 AD
While doing extensive research to defend Oneness Theology in my Church History debate with Roman Catholic Apologist William Albrecht in 2015, the Lord led me to read books written by Church Historians. That was when I found some startling information written by a Trinitarian Church Historian.
The Famed Church Historian Jaroslav Pelikan wrote in his book, The Emergence of the Catholic Tradition, Vol. 1, Pg. 207,
Marcellus of Ancyra “proved an embarrassment to Nicene Orthodoxy” because he and other “Sabellian” Monarchians were among “the signers in 325.”
The Emergence of the Catholic Tradition, Vol. 1, Pg. 207
According to Jaroslav Pelikan, a prominent Modalist Leader, Eustathius, the Bishop of Antioch, “reproached Eusebius for deviating from the Nicene faith, and (Eustathius) was charged in turn with Sabellianism (Modalism). Eustathius was accused, condemned and deposed at a synod in Antioch. The people of Antioch, always prone to disturbances, rebelled against this action …”
The Emergence of the Catholic Tradition, Vol. 1, Pg. 205-206
If Eustathius had merely signed the Nicene Creed in 325 because had compromised his views, why then would he have not compromised his views when he was condemned as a Sabellian? Thus there is strong evidence to believe that these early Modalists signed the Nicene Creed because they really believed that it was compatible to Modalism.
Eustathius would rather die of starvation in exile than to renounce his belief in the deity of Christ which he had affirmed at Nicaea in 325. Apparently, the majority of Eustathius’ followers also rejected the decisions of the State Church by rebelling against the removal of their leader into exile. Likewise, most modern Oneness Pentecostals also have strong convictions today. We would rather die than to obey men above God.
“After Eustathius had been removed, the Eusebians proceeded against Athanasius, a much more dangerous opponent. In 334 he was summoned before a synod in Caesarea; he did not attend, however, distrusting his opponents. In the following year he was again summoned before a synod in Tyre at which Eusebius presided. Athanasius, divining the result, went to Constantinople to bring his cause before the emperor. The emperor called the bishops to his court, among them Eusebius. Athanasius was condemned and exiled at the end of 335. At the same synod, another opponent was successfully attacked, Marcellus of Ancyra (q.v.) who had long opposed the Eusebians, and had only lately protested against the reinstitution of Arius.”
According to Pelikan, both Athanasius and Marcellus were both exiled by the Emperor Constantine at this time (about 335-337).
The Emergence of the Catholic Tradition Vol. 1 Pg. 207, by Jaroslav Pelikan
It is hard to imagine that Eustathius of Antioch and Marcellus of Ancyra were compromisers when they signed the Nicene Creed of 325. For if they had compromised their beliefs by signing the Nicene Creed, why then did they not compromise their beliefs when faced with exile in 334-335?
Eusebius, who had won the favor of Constantine, was able to convince the Emperor to turn his favor towards the Arians and semi-Arians. Constantine then reinstated Arius, and began persecuting those who believed in the deity of Christ. Hence, both the Oneness Modalists and the new Semi-Trinitarians were persecuted together as heretics by the Roman State Church.
Wherefore, the same Emperor Constantine who first convened and ratified the 325 Nicene Creed, later changed his mind by siding with the Arians and Semi-Arians. Hence, the persecution of the Arians ceased, while the persecution of the Modalists and Semi-Trinitarians began. Therefore the same Emperor Constantine who first exiled Arius and other bishops who refused to sign the Nicene Creed, later exiled Athanasius, Eustathius, and Marcellus for continuing to believe in the Nicene Creed. Therefore the historical evidence proves that the original Nicene Creed of 325 is not explicitly Trinitarian. Both Trinitarians and Oneness Modalists could affirm it.
Constantine died in 337, just two or three years after exiling Eustathius, Marcellus, and Athanasius for their belief in the deity of Christ.
Wherefore, the historical evidence proves that Modalists actually signed the original Nicene Creed of 325 A.D., but the same emperor who exiled the Arians in 325 A.D., later changed his mind by siding with the Arians about ten years later.
THE EARLY NICENE CREED AND THE WORD HOMOUSIAS
All that we know about the teaching of Sabellius comes from the writings of his opponents because his writings were later lost or destroyed by the Roman Catholic Church for alleged heresy. It is obvious that his detractors twisted and perverted his illustration of the sun and its rays as being God Himself. Christ is a mode of Being of the Father as a man. Although the man is lower than the God, the deity of the God who became the man is the same homousious (nature of Being) as the Father.
A Central Teaching of Sabellius Was Incorporated Into The Early Nicene Creed (325).
The historical evidence suggests that the Modalistic Monarchian idea of the "homoousious" of the Father and the Son being the same substance was incorporated into the Nicene Creed of 325 AD. That is why only the Arian heresy was rejected but not the theology of Modalistic Monarchianism.
Thomas Browning (a Graduate of Dallas Theological Seminary) stated that the modalistic monarchian theology of Sabellius was influential in the Nicene Creed itself.
"But the man most representative of modalistic monarchianism was a man named Sabellius (222 AD). Sabellius was much more sophisticated than Noetus ... Sabellius tried to solve the problem by using the illustration of the sun and its rays. The Father was the sun. Jesus is considered to be a dominate ray. He was projected for a while and then withdrawn back into the substance of the Father ... Sabellius could say Jesus was 'Light of Lights' and even 'homousias'. Jesus was 'Light of Lights' in that He was LIKE A RAY OF THE SUN, He emanated from the Father. He was 'homousias' in that he was of the same substance as the Father."
The History of the Doctrine of Justification, Chapter one "The Person of Christ" Post Tenebras Lux, Page 5 © 2010 Thomas R. Browning
Thomas Browning goes on to state on the same page,
"Now what’s interesting is the way the Nicene Creed uses these exact terms. If you will take a moment and turn in your hymnal to page 846, you will see the repetition of the very words that Sabellius thought so important” In the Nicene Creed!”
“THE NICENE CREED - We believe in one God, the Father Almighty, Maker of heaven and earth, of all things visible and invisible. And in one Lord Jesus Christ, the only‐begotten Son of God, begotten of his Father before all ages, God of God, Light of Light, very God of very God, begotten, not made, being of one substance with the Father; by whom all things were made; who for us and for our salvation came down from heaven, and was incarnate by the Holy Spirit of the virgin Mary, and was made man; and was crucified also for us under Pontius Pilate; he suffered and was buried; and the third day he rose again according to the Scriptures, and ascended into heaven, and is seated at the right hand of the Father; and he shall come again, with glory, to judge both the living and the dead; whose kingdom shall have no end.
Thomas Browning commented on the use of the exact wording of Sabellius in the Nicene Creed.
"If you will look at the seventh line, you will notice the phrase “light of light”. While in the ninth line, you will notice the phrase “being of one substance with the Father;” which is the English translation of “homousias”. Now what are we to conclude regarding those two phrases? It seems either the Nicene Creed is thoroughly Sabellian or something had occurred that was so gigantic in proportions that the church felt the need to go back to language that had been previously condemned in order to fight off whatever this new super threat happened to be (Arianism)."
Thomas Browning continues, "Now here is the interesting part. At the Council of Antioch (in 267), the church repudiated the idea of Christ being 'homousias' with the Father. They changed the phrase 'homousias to the phrase 'homoiousias'. The difference between the two words is extremely important, even though in Greek the difference between the two words is just one letter. The emphasis put on the difference of the one letter led Edward Gibbon to write in the Decline and Fall of the Roman Empire that never in the history of the world had there been so much energy spent over a single vowel."
The History of the Doctrine of Justification, Chapter one "The Person of Christ" Post Tenebras Lux, Page 6 © 2010 Thomas R. Browning
Although a small group of Christian leaders condemned Sabellius and Paul of Samasota at Antioch in 267 AD, the Roman Catholic Church was not developed into a single religious institution throughout the Roman Empire at this time. Therefore the church as a whole did not condemn Sabellius in 267, but only a small segment of professing Christian leaders in the vicinity of Antioch.
The historical evidence indicates that there were many Modalistic Monarchian Bishops who signed the original Nicene Creed in 325, such as Marcellus of Ancyra and Eustathius of Antioch. Marcellus and Eustathius were likely the prominent leaders of many Oneness believers throughout the empire just as Arius represented a larger group of many more like him.
Moreover, if the Arians were not also a very large group among the professing Christian multitudes, then why did Constantine change his mind and declare Arianism to be orthodox? Even Trinitarian historians point out that many of their early fathers were identified as “Semi-Arians” in that they believed that the Son was created and subordinate to the Father before his birth.
It is highly unlikely that the followers of men like Tertullian, Hippolytus, and Origen departed from their Semi-Arian theology. Just as Athanasius was a main representative for the Trinity, so Arius and Eusebius represented Arianism. Therefore only a few men were known as the leaders which represented each group at Nicaea.
It was not until the late fifth century that the Roman Catholic Church spelled out their later Trinitarian theology as "three coequal" and "three co-eternal" distinct divine "persons." It also happened to be the early to mid-fifth century that the Roman Catholic Church incorporated Mariology into its ecumenical Councils.
THE ORIGINAL NICENE CREED HARMONIZES WITH ONENESS THEOLOGY
The original Nicene Creed can be affirmed by Oneness Pentecostals (Modalists) as the creed was vague and could be interpreted in favor of Oneness theology. The only group that could not have affirmed that creed was the Arians.
"We believe in one God the Father All-sovereign, maker of all things." Oneness Pentecostals affirm!
"And in one Lord Jesus Christ, the Son of God, begotten of the Father, only-begotten, that is, of the substance of the Father," Oneness Pentecostals also affirm (Heb. 1:3)!
"God of God, Light of Light, true God of true God,"
With a correct understanding of God's omnipresence, Modalists could have agreed. The One true God the Father entered into a new existence by becoming a man. He was born as a human being so he can also be called "God of (from) God, Light of light, true God of true God." Modalists could have agreed with these words by affirming that the man Christ Jesus is also called God (but not two coequal God Persons). We have One true God the Father and one man who is also called that selfsame God because the Son is the "radiance" and "glory" of the Father's substance of Being as a human being. As long as we are not talking about two coequal and co-eternal God Persons Oneness Pentecostals could agree!
"begotten not made, of one substance with the Father,"
The human being called the Son of God was made (by his birth) but His deity could never have been made! Therefore the words, "begotten (born) not made" could be interpreted in favor of both Oneness and Trinitarian theologies. The Son was "made" by being born of a woman but He who became that child born and son given is the uncreated God Himself with us as a man. Thus the true identity of He who was begotten could never have been made. Hence Oneness Pentecostals affirm!